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Theory of structure and dynamics in condensed matter. Progress report, 1 April 1973--31 March 1974

Description: Work during the report period is summarized. Data and information are included from studies of the properties of disordered alloys and similar materials. Results are also included on the macroscopic engineering properties of polycrystalline or otherwise heterogeneous materials, theory and interpretation of heat pulse experiments and second sound in crystals, theory of neutron scattering from solid helium, studies of mechanisms of structural phase transitions, and dynamics of classical quadrupole solids. (auth)
Date: January 1, 1974
Creator: Krumhansl, J.A.
Partner: UNT Libraries Government Documents Department

Theory of structure and dynamics in condensed matter and applications in geophysics and solar energy. Progress report, 1 April 1975--31 March 1976

Description: The basic materials science objectives of the program have been met, and the theory built up over the past years on the properties of rocks and on the design of composite photothermal conversion surfaces has been tested. The major topics have been: (1) Theory of structural phase transitions; (2) Theory of interatomic interactions, with application to defect structures and surface complexes; and (3) Application of the theory of disordered (heterogeneous) materials to the elastic properties of rocks, commercial graphite, and composite solar energy absorbing materials. (WDM)
Date: March 1, 1976
Creator: Krumhansl, J. A.
Partner: UNT Libraries Government Documents Department

Fine scale mesostructures in superconducting and other materials

Description: We review experimental and theoretical literature on mesoscale features and structures in a variety of displacively transforming materials. These include twinning in martensites and the much finer scale tweed; both may have significant effects on both normal and superconducting properties. Elastic properties are particularly strongly affected. Recent x-ray neutron experiments suggest them in hi-{Tc} materials.
Date: January 1, 1992
Creator: Krumhansl, J.A.
Partner: UNT Libraries Government Documents Department

Fine scale mesostructures in superconducting and other materials

Description: We review experimental and theoretical literature on mesoscale features and structures in a variety of displacively transforming materials. These include twinning in martensites and the much finer scale tweed; both may have significant effects on both normal and superconducting properties. Elastic properties are particularly strongly affected. Recent x-ray neutron experiments suggest them in hi-{Tc} materials.
Date: July 1, 1992
Creator: Krumhansl, J. A.
Partner: UNT Libraries Government Documents Department

Fundamental theory of elastic wave scattering by defects in elastic materials: integral equation methods for application to ultrasonic flaw detection

Description: The use of ultrasonic methods in nondestructive testing depends on the interpretation of the scattering of sound waves by flaws. The theory of elastic waves and their scattering in non-uniform media is developed in detail from first principles, and in generality. Both integral equation and differential methods are discussed, with emphasis on the former. General methods for defining scattering cross sections are presented, and conservation theorems are noted. The Born Approximation to the integral equation is presented, and computed results for several experimental situations are discussed. Several corrections to papers in the literature are made, and in particular the exact scattering of a transverse wave by a spherical flaw is compared with the Rayleigh (long wave) limit.
Date: May 1, 1976
Creator: Gubernatis, J.E.; Domany, E.; Krumhansl, J.A. & Huberman, M.
Partner: UNT Libraries Government Documents Department

Nonlinear, distortive phenomena in solids: Martensitic, crack, and multiscale structures

Description: This ongoing program, from the beginning of the first three year grant 1988--1991 and now in the first year of the second phase 1991--1994, has been directed at developing both an understanding of the physics underlying structural transformations in real (alloy) materials as well as new theoretical methods which adequately describe the large (nonlinear) distortions which characterize such processes. We have had a particular interest in martensitic systems, first (1988--1991) in the equilibrium limits, and now (below) in phenomena associated with the transformation process.
Date: January 1, 1992
Creator: Krumhansl, J.A. & Sethna, J.P.
Partner: UNT Libraries Government Documents Department

Classical particle-like behavior of Sine--Gordon solitons in scattering potentials and applied fields

Description: We show that classical Sine-Gordon solitons maintain their integrity to a high degree in the presence of external perturbations. Two examples, of particular importance in condensed matter, are described in detail: (i) a model impurity is found to bind low-velocity solitons but merely phase-shift those with high-velocities, (ii) external static driving terms with damping accelerate the soliton to a terminal velocity. The importance of a translation mode is emphasized and it is concluded that the soliton behaves as a classical particle in all essential respects.
Date: February 1, 1976
Creator: Fogel, M. B.; Trullinger, S. E.; Bishop, A. R. & Krumhansl, J. A.
Partner: UNT Libraries Government Documents Department

Theory of nonlinear, distortive phenomena in solids: Martensitic, crack, and multiscale structures-phenomenology and physics. Progress summary, 1991--1994

Description: We have identified tweed precursors to martensitic phase transformations as a spin glass phase due to composition variations, and used simulations and exact replica theory predictions to predict diffraction peaks and model phase diagrams, and provide real space data for comparison to transmission electron micrograph images. We have used symmetry principles to derive the crack growth laws for mixed-mode brittle fracture, explaining the results for two-dimensional fracture and deriving the growth laws in three dimensions. We have used recent advances in dynamical critical phenomena to study hysteresis in disordered systems, explaining the return-point-memory effect, predicting distributions for Barkhausen noise, and elucidating the transition from athermal to burst behavior in martensites. From a nonlinear lattice-dynamical model of a first-order transition using simulations, finite-size scaling, and transfer matrix methods, it is shown that heterophase transformation precursors cannot occur in a pure homogeneous system, thus emphasizing the role of disorder in real materials. Full integration of nonlinear Landau-Ginzburg continuum theory with experimental neutron-scattering data and first-principles calculations has been carried out to compute semi-quantitative values of the energy and thickness of twin boundaries in InTl and FePd martensites.
Date: August 1, 1994
Creator: Sethna, J. P. & Krumhansl, J. A.
Partner: UNT Libraries Government Documents Department

Nonlinear, distortive phenomena in solids: Martensitic, crack, and multiscale structures. Progress report, 1991--1992

Description: This ongoing program, from the beginning of the first three year grant 1988--1991 and now in the first year of the second phase 1991--1994, has been directed at developing both an understanding of the physics underlying structural transformations in real (alloy) materials as well as new theoretical methods which adequately describe the large (nonlinear) distortions which characterize such processes. We have had a particular interest in martensitic systems, first (1988--1991) in the equilibrium limits, and now (below) in phenomena associated with the transformation process.
Date: August 1, 1992
Creator: Krumhansl, J. A. & Sethna, J. P.
Partner: UNT Libraries Government Documents Department